The cockney is a native of the East End of London. The original meanning of the word is "foolish person," [literally, "cock's egg" (i.e., malformed egg)].
The cockneys were considered a lower class novelty by the rest of London; a working class people with the worst English grammar in the English speaking world.
Nowadays the term cockney seems to apply to anyone from London. It has become a generic term for a Londoner.

Jock has several meanings. Across the Atlantic “jock” is usually associated with sportsmen - primarily football players.
In UK, it usually means a Scot. There is a slang and pejorative nickname defining each of the Celtic peoples: the Irish are "Paddies,"
(which is slang for Patrick); the Welsh are "Taffies" (a reference to being born within the sight of the river Taff in Wales), and the Scots are "Jocks."
(meaning "an innocent lad, a country boy.)" Most English or Sasanachs (Gaelic for Saxon) address Scots as Jock: "So what part of Scotland are you from, Jock?"
"Jock" is also used to mean a soldier. Soldiers can call each other Jock.

So "Cockney Jock" refers these days to a London-born Scot. Some say that to be a true cockney, one had to be born within the sound of the church bells of Bow in the East End of London.

"Cockney Jock" also refers to the London Scottish regiment:

The Highland Armed Association of London and The Loyal North Britons had been raised in 1793 and 1803 as part of the country’s Volunteer Forces ready to repel Napoleon’s threatened invasion of England.
These military groups were later disbanded and it was not until after the Crimean War that the country’s security seemed again to be in danger.
So, in 1859, sponsored by The Highland Society of London and The Caledonian Society of London, a group of individual Scots raised
The London Scottish Rifle Volunteers under the command of Lt Col Lord Elcho, later The Earl of Wemyss and March.
He decided to clothe the Regiment in Hodden Grey (*), the homespun cloth known throughout Scotland. This avoided all interclan feeling on the subject of tartan and,
as Lord Elcho said "A soldier is a man hunter. As a deer stalker chooses the least visible of colours, so ought a soldier to be clad."

(*) Hodden or wadmel is a coarse kind of cloth made of undyed wool, formerly much worn by the country folk of Scotland. It was usually home made on small hand-looms.
Grey hodden was made by mixing black and white fleeces together in the proportion of one to twelve when weaving. The origin of the word is unknown.

Nowadays known as the London Scottish (nickname Cockney Jocks) the formerly regiment, which served during the South African campaign and the two world wars, is now a company of The London Regiment.

“Cockney Jocks” was written in 1954 by Pipe/Sergeant Johnny Haynes of the Pride of Murray Pipe Band on hearing that the London Scottish Regiment was about to be disbanded.
The tune was played around Europe on their farewell tour and became a hit.
Johnny Haynes began playing the pipes in the Far East Air Force Band based in Singapore. Later, he joined the Pride of Murray pipe band.
He turned out for the London Scottish on various occasions with the Pipe Major of the Pride of Murray who had come from the Regiment.
Later he became the London Scottish Museum Curator. When he retired, Johnny joined the Surrey Pipe Band, at the same time being Pipe Sergeant of the London Irish Rifles.

Colin Robertson, Director of the Scottish National Dance Company, choreographed a dance to fit the tune. He taught it in the US around 1980’s when conducting some dance workshops.
Cockney Jocks is a rather unusual Highland Dance because it is lyrical and many of the dancers’ positions are held for more than the normal one count of music. Gaelic Fusion dance company
took the already intriguing dance performed by an individual dancer and modified the steps to work as a group. The ever changing pairings or
groupings of dancers is a tribute to the proud cockney jocks regiment.